Trying to achieve this Water effect

I'm searching the unity forums and questions the whole weekend and didn't find any explanations or examples. As reference, click on this webgl water demo link ->

http://madebyevan.com/webgl-water

I know, someone already asked something similar here -> http://forum.unity3d.com/threads/beautifull-webgl-water.100649/

And the answer was: "without a problem and at a much higher performance."

My question: Unity has water, that is only visible from the top view, it's invisible from the side.

You could say, just add a transparent plane to the sides(green line)...yes, but then, the upper face(red line) of the plane, won't animate with the water like in the demo.

How can I create in unity such a cube of water, animated at the top, reacting when something falls in and sides are closed? Even from below, the watersurface is visible and shiny.

edit: And yes, I already read this: http://answers.unity3d.com/questions/676223/how-to-render-a-block-of-water-.html As I already wrote, a simple plane from the side isn't possible, it will cross the water surface while it moves or leave wholes..

edit2: if I move the ball along the wall, I can see, this water has no side planes, it's seems to be just a script, uses the watermesh as a mask and tints everything below it, bluish. It's only a guess. For the reflection underwater I need the 'FX/water Grabpass' shader, pro only. Why I find those answers not until I asked here. Now only finding out how to tint the area below the mesh, along the animated vertices.

I can't be a light culling mask? The ball can be half underwater and half above..